1. Field of the Invention
The present invention generally relates to a method and a device for controlling subscriber data of mobile stations in a mobile-communication system, and particularly relates to a method and a device for controlling subscriber data which store or delete subscriber data of mobile stations in or from a visitor location register of a cellular-mobile-communication system.
2. Description of the Related Art
FIG. 16 is an illustrative drawing showing a configuration of a cellular-mobile-communication system. A cellular-mobile-communication system includes a home-location register HLR, a visitor-location register VLR, a mobile-service-switching center MSC, base stations BSS, and mobile stations MS.
The home-location register HLR stores subscriber data (mobile customer data) such as an identification number, a location, and an identification key with respect to each of the mobile stations MS covered by a home network. The home-location register HLR transmits subscriber data to a visitor-location register VLR of a given area when a mobile station MS moves to this area.
The visitor-location register VLR receives and stores the subscriber data of each mobile station MS residing in its area of control when the home-location register HLR of each mobile station MS transmits the subscriber data.
The mobile-service-switching center MSC receives a location-update request from the mobile stations MS via the base stations BSS, and requests the visitor-location register VLR to attend to location-update processing. Further, the mobile-service-switching center MSC attends to switch control of receipt and transmission of calls with respect to the location-registered mobile stations MS via the base stations BSS.
FIG. 17 is a flowchart of a process of registering a location. FIGS. 18A through 18E are illustrative drawings showing data structures of messages and data which are exchanged during the process of registering a location.
When a mobile station MS moves from a wireless service area to another wireless service area, or when a power switch of a mobile station MS is turned on, the mobile station MS receives information on the wireless service area sent from the base station BSS. When the mobile station MS detects that the received information is different from information stored in the mobile station MS, the mobile station MS transmits a signal requesting updating of a location.
Upon receiving the signal for requesting location update, the base station BSS transmits a location-update-request message 13-1 to the mobile-service-switching center MSC (step S12-1 in FIG. 17).
Upon receiving the location-update-request message 13-1, the mobile-service-switching center MSC transmits an authentication-request message to the visitor-location register VLR in order to check if the mobile station MS that requested location update is a legitimate registered station (step S12-2).
Upon receiving the authentication-request message, the visitor-location register VLR searches for a home-location register HLR that is home to the relevant mobile station MS. This search is made based on a mobile identification number of the mobile station MS. Then, the visitor-location register VLR sends the authentication-request message to the home-location register HLR that is found in the search (step S12-3).
In response to the authentication-request message, the home-location register HLR refers to the subscriber data of the mobile station MS by using the mobile identification number, and notifies the visitor-location register VLR of an authentication-request acknowledgement (step S12-4).
The visitor-location register VLR forwards the authentication-request acknowledgement to the mobile-service-switching center MSC (step S12-5).
In accordance with the authentication-request acknowledgement, the mobile-service-switching center MSC transmits a registration-notification message 13-2 to the visitor-location register VLR (step S12-6).
Upon receiving the registration-notification message 13-2 from the mobile-service-switching center MSC, the visitor-location register VLR forwards the registration-notification message 13-2 to the home-location register HLR (step S12-7).
In response to the registration-notification message 13-2 sent from the visitor-location register VLR, the home-location register HLR reads subscriber data of the relevant mobile station MS from a subscriber-data-storage area 13-3, and sends a subscriber-data message 13-4 to the visitor-location register VLR (step S12-8).
The visitor-location register VLR stores the subscriber data of the relevant mobile station MS sent from the home-location register HLR, and notifies the mobile-service-switching center MSC of a registration-notification acknowledgement (step S12-9).
Upon receiving the registration-notification acknowledgement from the visitor-location register VLR, the mobile-service-switching center MSC informs the base station BSS of a result of the location update (step S12-10).
With reference to FIG. 18A, the location-update-request message 13-1 includes a mobile identification number and a mobile-station electronic serial number of the relevant mobile station MS as well as a base-station ID of a wireless service area where the mobile station MS is currently located. The location-update-request message 13-1 is sent from the base station BSS to the mobile-service-switching center MSC.
With reference to FIG. 18B, the registration-notification message 13-2 includes the mobile identification number and the mobile-station electronic serial number of the relevant mobile station MS as well as a mobile-service-switching-center ID of the wireless service area where the mobile station MS is currently located. The registration-notification message 13-2 is sent from the mobile-service-switching center MSC to the visitor-location register VLR and from the visitor-location register VLR to the home-location register HLR.
With reference to FIG. 18D, the subscriber-data-storage area 13-3 of the home-location register HLR stores a mobile identification number, a mobile directory number, location information including a mobile-service-switching-center ID of an area of a current location, a priority parameter, etc., with respect to each mobile station MS that belongs to the home network.
The priority parameter indicates priority that is given to a subscriber service class of a relevant mobile station MS. The priority parameter may range from 0 to 15, for example, as shown in FIG. 18E.
With reference to FIG. 18C, the subscriber-data message 13-4 includes the mobile identification number, the mobile-service-switching-center ID, the mobile directory number, and the priority parameter. The subscriber-data message 13-4 is sent from the home-location register HLR to the visitor-location register VLR as a response to the registration notification, and is stored in the visitor-location register VLR.
The subscriber data stored in the visitor-location register VLR is generally deleted when the mobile station MS moves to another wireless service area. The deletion of the subscriber data is prompted by a notice sent from the home-location register HLR when a visitor-location register VLR of the new wireless service area receives and stores the subscriber data in response to a location-update request.
FIG. 19 is a flowchart of a process of deleting a location update. Here, a new visitor-location register VLR is one that is provided in an area into which the mobile station MS moves, and an old visitor-location register VLR is one that is provided in an area from which the mobile stations MS moves out. The old visitor-location register VLR has subscriber data of the mobile station MS stored therein.
From steps S14-1 to S14-7, a process of updating a location is performed with respect to the new visitor-location register VLR in the same manner as in the steps S12-1 through S12-7 of FIG. 17.
Upon receiving the registration-notification message from the new visitor-location register VLR, the home-location register HLR searches for the old visitor-location register VLR by referring to the information on the visitor location stored in the subscriber-data-storage area. Then, the home-location register HLR transmits a registration-cancellation message to the old visitor-location register VLR (step S14-8).
Having received the registration-cancellation message, the old visitor-location register VLR deletes the subscriber data of the relevant mobile station MS, and transmits a registration-cancellation acknowledgement (step S14-9).
The home-location register HLR receives the registration-cancellation acknowledgement from the old visitor-location register VLR, and, then, sends the subscriber data to the new visitor-location register VLR (step S14-10).
Steps S14-10 through S14-12 of FIG. 19 are the same as the steps S12-8 through S12-10 of the location-update process shown in FIG. 17, and a duplicate description thereof will be omitted.
As described above, each time a mobile station MS moves from a wireless service area to another wireless service area, a process of registering subscriber data needs to be performed with respect to a visitor-location register VLR of the new wireless service area. Further, the subscriber data of the relevant mobile station MS needs to be deleted from a visitor-location register VLR of the old wireless service area.
A visitor-location register VLR has only a limited memory area for storing subscriber data. since the number of mobile stations MS residing in a given area is a matter of random occurrence, a given visitor-location register VLR may receive an excessively large number of location-update requests issued from mobile stations MS. In this case, the visitor-location register VLR may have the subscriber-data-storage area thereof completely full of data, and cannot store new subscriber data. Such a visitor-location register VLR simply rejects new requests for location update in excess of the number of mobile stations MS that can be accommodated therein. A mobile station MS, which is rejected after issuing a request for location update, cannot receive a communication service.
Accordingly, there is a need for a scheme which can improve a success rate of location update when a location update is requested by a mobile station MS that belongs to a service class having high priority.
Accordingly, it is a general object of the present invention to provide a scheme which can achieve the need described above.
It is another and more specific object of the present invention to provide a scheme which can improve a success rate of location update when a location update is requested by a mobile station MS that belongs to a service class having high priority.
In order to achieve the above objects according to the present invention, a method of storing subscriber data in a mobile-communication system includes the steps of providing a high-priority-subscriber-storage area in addition to an ordinary-subscriber-storage area, and storing subscriber data of a relevant subscriber in the high-priority-subscriber-storage area if priority of the relevant subscriber exceeds a predetermined threshold and if the ordinary-subscriber-storage area is full.
The method described above utilizes information about priority of subscribers, and gives precedence to subscribers having priority exceeding the predetermined threshold so as to secure a place for storing the subscriber data of such subscribers in the high-priority-subscriber-storage area. This improves a success rate of location update (i.e., success rate of storing subscriber data) when a location update is requested by a subscriber using a mobile station MS that belongs to a service class having high priority.
According to another aspect of the present invention, a method of deleting subscriber data of a mobile station in a mobile-communication system includes the steps of checking priority of a mobile station when receiving a message indicating either a power down of the mobile station or a completion of a call by the mobile station, keeping subscriber data of the mobile station if the priority of the mobile station exceeds a predetermined threshold, and deleting the subscriber data of the mobile station if the priority of the mobile station does not exceed the predetermined threshold.
The method described above utilizes information about priority of mobile stations, and determines whether to delete subscriber data based on whether the priority of a relevant mobile station exceeds the predetermined threshold. Therefore, a mobile station having priority exceeding the threshold can keep its subscriber data registered in the system even when the mobile station is switched off or a call is completed.
According to another aspect of the present invention, a method of storing subscriber data in a mobile-communication system includes the steps of storing subscriber data of a relevant subscriber in a data-storage area if there is a space therein, and replacing subscriber data of another subscriber in the data-storage area with the subscriber data of the relevant subscriber if the data-storage area is full and if priority of the relevant subscriber exceeds a predetermined threshold, said another subscriber having lower priority than the relevant subscriber and being currently not on phone.
The method described above utilizes information about priority of subscribers, and gives precedence to subscribers having priority exceeding the predetermined threshold when registering the subscriber data of the subscribers in the data-storage area. This improves a success rate of location update (i.e., success rate of storing subscriber data) for subscribers using mobile stations MS that belong to service classes having high priority.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.